A typical RF-type cable, including coaxial, twin-axial, and triaxial cable, comprises at least one inner conductive wire, a surrounding conductor (braid), a dielectric insulating layer disposed between the conductor and the braid, and an outer insulating jacket. Such cables are usually connected to devices using connector assemblies crimped or soldered onto the cable end. The RF connector is screwed onto a metal panel and is mated to a receiving connector. With the above arrangement, however, it was found that electrical noise could pass directly into the connector shell from the metal panel, causing interference. It was therefore advantageous to provide a filter adapter which could be inserted between the cable/connector assembly and the mounting chassis of the device to which it is attached to filter out the electrical noise and provide DC isolation.
One device for doing the forgoing is described in U.S. Pat. No. 5,032,091. The adapter described therein includes an insulating, three shouldered gasket having a small capacitor disposes in a channel formed therein. The gasket isolates the electrical connector from the receiving connector so that all ground currents transferred between the electrical connector and the receiving panel can only pass through the filter. It was found, however, with this apparatus that, due to the small contact area of the filtering device with the connector and panel, the filter could not operate at frequencies above 300 Mhz. In addition, the apparatus required that the small capacitor be epoxied into the housing, resulting in a significant increase in assembly time and a higher failure rate.